Image guided medical and surgical procedures utilize patient images obtained prior to or during a medical procedure to guide a physician performing the procedure. Such procedures can be referred to as computer assisted procedures. Recent advances in imaging technology, especially in imaging technologies that produce highly-detailed, two, three, and four dimensional images, such as computed tomography (CT), magnetic resonance imaging (MRI), fluoroscopic imaging (such as with a C-arm device), positron emission tomography (PET), and ultrasound imaging (US) has increased the interest in image guided medical procedures.
Typical image guided navigation systems generally require a dynamic reference frame to track the position of the patient should patient movement occur during the assisted procedure. The dynamic reference frame is generally affixed to the patient in a generally permanent or immovable fashion. The dynamic reference frame may also be used as a fiducial marker and may, therefore, be attached to the patient during the acquisition of pre-operative images. This enables the image space to be aligned with patient space during the navigated procedure.
Various instruments that are desired to be tracked may be used during an operative procedure. Image data is generally acquired, either intra-operatively or pre-operatively, and the instrument is generally illustrated, and superimposed on the captured image data to identify the position of the instrument relative to the patient space. Therefore, the instrument may include tracking sensors, such as electromagnetic coils or optical detection points, such as LEDs or reflectors that may be detected by a suitable tracking system. Also, a dynamic reference frame (DRF) can be used by the tracking system to maintain a registration or localization of the patient space to the image space. The DRF can be also any appropriate tracking sensor that is fixed to a portion of the patient that allows the system to determine whether the patient has moved relative to the image space.
Other types of navigation systems operate as an image-less system, where an image of the body is not captured by an imaging device prior to the medical procedure, such as the device disclosed in U.S. patent application Ser. No. 10/687,539, entitled Method And Apparatus For Surgical Navigation Of A Multiple Piece Construct For Implantation, filed Oct. 16, 2003, incorporated herein by reference. With this type of procedure, the system may use a probe to contact certain landmarks in the body, such as landmarks on bone, where the system generates either a two-dimensional or three-dimensional model of the area of interest based upon these contacts. This way, when the surgical instrument or other object is tracked relative to this area, they can be superimposed on this model.
Generally, regardless of the whether the system is using images or imageless, a dynamic reference frame is used to maintain registration of the patient space with the navigated or image space. The position of the patient can be determined in real time relative to the images, implant, instruments, etc. with the use of a dynamic reference frame.
Most types of orthopedic medical procedures are performed using conventional surgical techniques, such as spine, hip, knee, shoulder, a synovial joint, and a facet joint. These techniques generally involve opening the patient in a manner to provide adequate viewing by the surgeon during the medical procedure. Use of the navigated procedure may enable more precise and accurate placement of an implant within the patient and may also enable surgery with diminished visualization.
Although a dynamic reference frame can be attached to an external or skin portion of a patient, it may be desirable to attach the dynamic reference frame to a bone portion. Nevertheless, it is desirable to allow the dynamic reference frame to be easily yet fixedly attached to the patient. It may also be desirable to fix the dynamic reference frame to the patient with a single member in an easy or simple procedure.